This invention relates to a rear wheel steering apparatus. More particularly, this invention relates to a rear wheel steering apparatus having a neutral return means for manually returning rear wheels to a neutral position in the case of the failure of an electric motor or an electric control device.
A conventional rear wheel steering apparatus of this kind is disclosed in, for example, U.S. Pat. No. 4,703,945. This apparatus includes an electric motor, a rotational member rotated by the electric motor, a tie rod connecting member for converting a rotational movement of the rotation member into a movement in the direction of a width of the vehicle, a connecting member provided between the rotational member and the tie rod connecting member and able to be driven conversely by an external force from the rear wheels and an engage means provided on the rotational member and being engageable with a manual rotation means for manually giving a rotational movement to the rotational member.
In the above mentioned prior apparatus, in case it is possible to rotate a rotational shaft of the electric motor from outside, it is possible to rotate the rotational member by the manual rotation means and thereby the rear wheels can be returned to a neutral position. However, it must depend on intuition of an operator whether the rear wheels were returned to the neutral position or not. Therefore, it is necessary to repeat the running of the vehicle after the rotation of the manual rotation means in order to confirm the going straight ahead of the vehicle and the efficiency of the operation is low.
A need exists for a rear wheel steering apparatus which can return the rear wheels to the neutral position efficiently.
A rear wheel steering apparatus comprises an electric motor for generating a rotational torque, an electric control device for controlling the rotation of the electric motor, a motion converting means for converting the rotational torque of the electric motor into a propulsion force in the direction of a width of a vehicle and connected to a rotational shaft of the electric motor, an output shaft for outputting the propulsion force in the direction of the width of the vehicle which is converted by the motion converting means, tie rods connecting between the output shaft and rear wheels and having a ball joint, respectively, a housing fixed to the vehicle and accommodating the electric motor, the motion converting means and the output shaft therein, a rear wheel steering angle detecting means for detecting a steering angle of the rear wheels steered by the output shaft, a regulating member connected to the housing and for prohibiting the output shaft from rotating while allowing the output shaft to move in the axial direction, a neutral return means for manually returning the rear wheels to a neutral position in the case of the failure of the electric motor or the electric control device, a neutral return detecting means for detecting the return of the output shaft to the neutral position and a neutral return notification means for notifying the return of the output shaft to the neutral position.